The present invention relates to covers or tarping systems for open-topped containers. More specifically the invention relates to a system for the deployment of such covers over the container body.
Most hauling vehicles, such as dump trucks, include open-topped containers used for hauling or storing various materials. For example in a typical dump truck application, the dump body is used to haul a variety of particulate material, such as gravel, aggregate or similar products.
Depending upon the nature of the material stored in the open-topped container, it is usually desirable to provide a cover for the container. The industry has gravitated toward flexible tarping systems that can be wound and unwound from a spool to cover the container top. The flexible tarpaulin can be easily stowed at the front of the vehicle when the cover is not necessary, such as when the dump bed is being loaded.
A variety of tarping systems have been developed that are geared to a wide range of hauling vehicle applications. One such system for use with dump trucks is the Easy Pull(copyright) Tarping System of Aero Industries, Inc. The Easy Pull(copyright) System includes a flexible tarp that is wound around a spool at one end of the dump bed. A rope attached to the free end of the tarp can be used to unwind the tarp from the roller to extend the length of the bed. The spool can include a torque spring that provides a recoil or return force to wind the tarp around the spool when it is no longer in use.
Another cover system particular suited for open-topped containers is the Easy Covers(copyright) System, also of Aero Industries, Inc. The Easy Cover(copyright) Tarping System includes a U-shaped bail member that is pivotably mounted at its ends to the base of the container body. The horizontal section of the U-shaped bail member is attached to the tarp. In one application of the Easy Cover(copyright) Tarping system, pulling the horizontal bar of the U-shaped bail member using a rope can manually deploy the tarp. Again, the tarp can be wound onto a spring-biased spool at the front end of the dump bed.
As with many flexible tarping systems, the Easy Cover(copyright) System can include an actuation mechanism that automatically pivots the U-shaped bail member to deploy the tarp over the load of the open-topped container. One common deployment mechanism is a series of springs connected to the base of the U-shaped bail. One example is depicted in FIG. 1. Specifically, a vehicle 10 includes an open-topped body 11 covered by a flexible tarpaulin 13. The tarp 13 can be wound onto a tarp roller 14 situated at the front of the vehicle bed.
A bail member 16 is connected to the free end of the tarp. An actuation or deployment mechanism 17 can be used to mount the base of the bail member 16 to the vehicle bed 11. The actuation mechanism 17 can take many forms. For instance, the mechanism can comprise the torsion springs discussed above. In another version, a hydraulic cylinder-driven rack and pinion mechanism is utilized. In a more direct system, a hydraulic cylinder is mounted to the outside of the vehicle body 11 and actuated to forcefully pivot the bail arms relevant to the truck body.
In another version depicted in FIG. 2 a hydraulic cylinder mechanism is mounted to the underside of the vehicle bed. Specifically, a hydraulic actuator 20 is pivotably mounted to a lower vehicle frame member 23 by way of a pivot mount 24. The hydraulic actuator 20 includes an extension rod 26 that reciprocates within the cylinder of the actuator. A bracket 27 is mounted to the free end of the extension rod 26. This bracket is pivotably attached to an actuation lever 28 that is connected to an arm of the bail member 16 by a pivot pin 29 passing through the vehicle frame member 23. The pivot pin 29 is specifically configured so that the bail member arm 16 pivots with the actuation lever 28.
In operation, as the extension rod 26 is withdrawn into the actuator 20, it causes the actuation lever 28 to pivot, which ultimately causes the bail member 16 to pivot. With this configuration, the hydraulic actuator and actuation mechanism extends below the bottom of the vehicle body 11. Moreover, two such actuators are often required, one for each side of the vehicle. Furthermore, the system depicted in FIG. 2 relies upon the length of the actuation lever 28 to provide a moment arm to generate sufficient torque while pivoting or rotating the bail member 16. Finally, systems of this type are highly susceptible to the harsh environment existing underneath the truck bodyxe2x80x94namely, dirt, water and impact damage.
There is therefore a need for a deployment mechanism for use with a flexible tarping system that can be easily and compactly installed on a truck body. In addition, there is need for such a system that is protected from the elements, and that is capable of generating sufficient amounts of torque to deploy flexible tarps of various lengths.
In order to address the needs left unfulfilled by prior devices, the present invention contemplates a hydraulic rotary actuator that is generally centrally mounted on the underside of the container body. The actuator is connected by a pair of half shafts to the legs of the bail member to permit the transmission of rotational motion and torque from the actuator to the bail member. The rotary actuator is in the form of a compact elongated cylinder that is less susceptible to the harsh environment at the vehicle undercarriage.
In one feature, the rotary actuator includes a pair of half shafts that are connected to opposite ends of an actuation shaft. The actuator also includes a piston disposed in within the cylinder chamber that divides the chamber into two portions. Each portion includes its own fluid inlet that can be alternatively connected to a source of pressurized fluid. A helical spline arrangement is defined between the piston and the actuation shaft so that linear movement of the piston results in rotation of the actuation shaft. The linear movement of the piston is calibrated to produce a pre-determined amount of rotation of the actuation shaft, which ultimately corresponds to sweeping the bail member through an appropriate arc to fully deploy the cover.
In a further aspect of the invention, a control valve system is provided between the fluid inlets to the hydraulic rotary actuator and the source of pressurized fluid. Preferably, the source is the vehicle hydraulic system. The control valve system can include flow control valves associated with each inlet that are operable to vary the fluid flow rate from each inlet. This metered out flow rate can control the rate of rotation of the actuation shaft, and ultimately the bail member, in the deployment and retraction directions. The control valve system also includes a manually controllable three-position four-way solenoid valve that controls the flow of fluid into and out of the two inlets. In one embodiment, the solenoid valve connects or disconnects one inlet from the fluid source, and either closes or opens the second inlet to drain.
One benefit of the present invention is that the deployment or actuation mechanism for the tarping system is capable of providing torque directly to the bail member. Another benefit is that the actuator can be mounted to the underside of the container body in an orientation that helps protect the actuator from the elements.
A further benefit is that the rotary actuator aspect allows the actuation mechanism to maintain a reduced envelope beyond the sides of the vehicle to readily comply with various vehicle size regulations. Still another benefit is that the hydraulic actuator can accommodate a wide range of bail arm sweep angles depending upon the geometry of the truck body. Other benefits and certain objects of the invention will become apparent upon consideration of the following written description and accompanying figures.